Pescadero Unconformity EarthCache
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Unconformities
An unconformity represents a gap in the geological record where a
younger strata of rock comes in direct contact with a much older
strata. There are three kinds of unconformities each refers to the
plane of juncture or where the two strata come into contact with
each other.
Disconformity: Where the discontinuous strata are parallel to each
other. This usually represents a period of erosion or
non-deposit.
Non-Conformity: Where sedimentary rock has been deposited onto
metamorphic or igneous rocks. The plane is usually irregular.
Angular Unconformity: Where the discontinuous strata meet each
other at an angle. This usually is the result of the older strata
being uplifted through the younger due to some geologic
activity.
Pescadero State Beach
Pescadero State Beach is actually three separate beaches each with
its own character.
The northern beach is what most of us think when we hear beach. It
has a wide sand and beautiful view out to the open ocean.
The middle beach is a wide shallow cove with a sand and pebble
beach. If you come at extreme low tide there are tidal pools to
explore.
The southern beach is a small deeper cove with a rock beach.
The coordinates for this cache will take you to the cliff arm at
the south of this southern beach.
Pescadero Unconformity
You are standing on top of the Pescadero Unconformity.
If you turn to the north and look at the cliff face what you are
seeing is sandstone and other material from the Oligocene
Age.
When you turn to the south and look at the cliffs what you are
seeing is the beginning of the Pigeon Point Formation which
stretches approximately 10 miles south to Año Nuevo. This formation
is from the late Cretaceous Age.
This unconformity is an Angular Unconformity, where the younger
era's deposits lie at a different angle from those of the the older
era.
To log this cache you must answer the following questions to me in
an email. You may need to walk around to get a good view of each of
the cliffs:
1. Looking to the cliff to the south of the arm you are standing
on, describe the layering you see there.
2. Looking to the cliff face to the north of the arm you are
standing on, at about the middle of the beach, describe the
layering you see there. You can get quite close to examine this if
you wish via the stairs down by the cliff face.
3. Approximately how many million years is the gap in the geologic
record between these two cliffs?
4. To get to the coordinates from the parking lot you had to walk
down a flight of steps. How many steps are there and what 2
materials are these steps primarily composed of.
Be sure to include the names of everyone in your caching
group.
Please feel free to post pictures of your group, but please do not
post pictures of the cliffs.
Pescadero State Beach is open from 8:00 am to Sunset. Please
observe these rules.
If you have time, I highly recommend also visiting the Pescadero
Marsh Natural Preserve on the other side of the highway.
This is a very safe place to stand, but be aware that it can get
very gusty at times and in very high surf, there is even the remote
possibility of getting wet. Even in summer a light jacket is
recommended.
UNDER NO CIRCUMSTANCE SHOULD THIS CACHE BE ATTEMPTED DURING A
STORM.
Additional Hints
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